The present invention is directed to a scanner for measuring at least one parameter of a sheet material such as the basis weight or moisture content of paper and, more specifically, to a scanner which has a dust belt which protects a gauging head which is contained entirely within a tubular beam suspended across the sheet material.
For the measurement of the properties or parameters of a moving paper sheet a pair of gauging heads are used which scan the sheet of material in a cross direction (CD) with material moving in a machine direction (MD). The gauging heads themselves are mounted on a pair of spaced upper and lower beams as more fully disclosed or shown in the above pending application. Normally, the gauging heads are external to the beams which are in a cross direction across a moving paper sheet and since the gauging head operates in an extremely hot or moist environment, cooling water or cooled air must be supplied by a separate unit in the beam to the gauging heads. Also, the upper and lower gauging heads must move in perfect synchronism to reduce measurement errors.
It is a general object of the present invention to provide an improved scanner for measuring at least one parameter of a sheet of moving material.
In accordance with the above object, there is provided a scanner for measuring at least one parameter of a sheet of material moving in a machine direction(MD) including gauging head means mounted for cross direction (CD) movement across the sheet, and perpendicular to the MD, from one edge of the sheet to the other comprising at least one tubular beam suspended over or under the sheet in the CD from one the edge to the other, the beam having a continuous slot in the CD in proximity to such sheet to allow the gauging means to measure the parameter. Guide means are inside the tubular beam on which the gauging head means is interiorly mounted for CD movement within the tubular beam, such gauging head means having a face exposed through the slot to the sheet without physical interference for measuring a the parameter of the sheets. Seal belt means are substantially contained within the tubular beam and connected to the gauging head for sealing the length of the slot in the CD to protect the interior of the beam and the gauging head from ambient dust, dirt, and air, the sealing belt means including an opening at the gauging head to allow direct communication, without interference, between the gauging head face and the moving sheets. Means are provided for driving the gauging head in the CD.